University of Reading
Atmospheric Observatory
Hottest by day.
Hottest by night.
June 2026 has rewritten the observatory's record on both counts. The peak of 34.9 °C on the 24th is the hottest June day in 118 years — beating the old mark of 34.0 °C set in 1976 — and the temperature passed 34 °C on four days running, a streak never recorded here in any month. After dark it went further: the nights of the 25th and 26th, at 20.9 °C and 21.3 °C, are the two warmest ever logged on this site.
Three shapes of a heatwave
Heat never arrives the same way twice. 1976 was a marathon of hot days under clear skies that fell cool each night; 2022 was a single violent spike that broke within a day; 2026 stacks hot days and hot nights back to back. Pick an event to set it beside this week.
More than sixty hours above twenty
Five-minute readings let us ask a sharper question: how long did the air stay continuously above 20 °C, never once dropping back? In a normal summer the answer is a single afternoon — the heat breaks every night. This June it held for more than two and a half days, riding straight through three nights, before finally dropping back below the line at 27 Jun 01:15. The following night then bottomed out at 18.1 °C at 27 Jun 04:40.
24 Jun 04:40–27 Jun 01:15 · the longest in the five-minute record
Year by year
Longest unbroken spell above 20 °C each year in the five-minute record. Most years manage a single hot day before the night breaks it; only 2020 and 2026 carried the heat through more than one night.
Tropical nights barely existed — until now
A tropical night never drops below 20 °C. In the whole twentieth century the observatory logged just two — one in 1949, one in 1995. The 2020s alone hold six, and the two warmest of all fall in this single week.
Nights at or above 20 °C per decade, any month · Reading University Atmospheric Observatory.